Corrosion prevention



CORROSION PREVENTIQN Howard F. Keller, Jr., Fullerton, Califi, assignor to Union Oil Company of California, Los Angeles, Calif., a corporation of California No Drawing. Application October 8, 1956 Serial No. 614,374

16 Claims. (Cl. 2528.'55)

This invention relates to corrosion prevention, and in particular concerns compositions and methods for preventing corrosion in oil wells.

In many of the oiland gas-producing areas .of the United States, the production of crude oil and gas is accompanied by the production of aqueous brinesrcontaining dissolved carbon dioxide and/or hydrogen sulfide. Such brines are highly corrosive with respect to ferrous metals, and are responsible for frequent failures of metallic equipment associated with the well, e. g., the welltubing and easing, sucker rods and sucker rod boxes, pump parts, gathering lines, etc. ,In numerous instances the corrosion damage is so severeasto require replacement of sucker rods and pump parts as often as ,once a month and replacement of at least part of the tubing string as often as once a year. The cost of such replacement, together with the cost of constant inspection and the loss of production during ,the frequentperiods when the well is shut down forrins pection or-replacementof parts, is a major factor in the cost-of the oil and/ortgas zproduced. Among those who have beenmost closely associated with the problem of preventing corrosion in oil and gas wells it is generally conceded that the most satisfactory solution lies in the use of chemical corrosion inhibitors which can .be introduced directly into the well and admixed with the well fluids before .the .latter can .come in .contact with metallic .wellequipment. However, many of the materials .which have been Lproposed .for such use have not been satisfactory in actual practice, particularly where relatively high temperature conditions prevail (as in deep wells when the bottom hole temperature often exceeds 100 C.) and/oracidic gases such as carbon dioxide and/ or hydrogenisulfide are present.

It is accordingly an object of the present invention to provide improved means for preventing the corrosion of ferrous-metals inoil and gas wells.

Another object is to provide means for preventing cor- 'rosion induced by oil apd/ or gas well br-incs in :the presence .of carbon dioxide and/tor hydrogen sulfide at the elevated temperatures and pressures which :exist within relatively deep wells.

A further object is to provide improved corrosion .inhibitors for use in oil wellsand the like.

Other and related objects will be apparent from the following detailed description of the invention, and various advantages not specifically'referred to herein will occur those skilled in the art upon employment of the invention in practice.

I have now found that the above objects and attendant advantages may be realized through the provision and .use of corrosion inhibiting compositions comprising as the essential vactiveingredient ,a reaction product of a certain type of vinyl ester anda-polyethylene polyamine. More particularlyl have found that theproducts obtained by reactinga vinyl esteriofa fatty acid containing from about 12 to about .22 carbon atoms withat least one mo- States Patent A 2,824,835 Patented Feb. 25, 19.58

ice

wherein "x represents an integer from 1 to 5, can be dis solved or dispersed in well fluids to inhibit the corrosion thereby of ferrous metals to a remarkable extent under exceptionally adverse conditions of temperature and pressure, and in the presence of acidic gases such as carbon dioxide and hydrogen sulfide. The effectiveness of these products against hydrogen sulfide corrosion is to some extent unique since many materials which are somewhat effective in the presence of carbon dioxide are substantially useless in the presence of hydrogen sulfide. The present-products are effective in very small amounts, and may be directly introduced into the Well bore as such or, more preferably, in the form of a solution of 20-80 percent by weight concentration in alight petroleum hydrocarbon or other suitable inert solvent. As is hereinafter more fully explained, they may advantageously be employed in conjunction with dispersing agents adapted to promote dispersion in both the aqueous and oil phase of the well efiluent. In addition to their corrosion inhibiting properties, the present products are surface active, and their presence in well efliuents promotes deniulsification of the same. 7 l

The composition of the present-class of corrosion inhibitors cannot be accurately defined. The process by which they are made involves a reaction between the vinyl groups of the vinyl ester and the amino group of the ethylene polyamine:

wherein R represents an aliphatic radical containing from 11 to 21 carbon atoms. However, when the ethylene polyamine reactant contains both primary and secondary amino groups'it is not known which is the -n1orereactive and it is hence not known at what point the group is attached to the ethylene polyamine molecule. Very probably, the reaction product comprises a mixture of individual compounds. Furthermore, in order to attain the proper degree of oilandwvater-solubility or dispersibility, it is preferred that only between about 2 and about 3 moles of the vinyl ester be combined with each mole of the ethylene polyamine. Accordingly, when the number of amino groups in the ethylene ,polyamine exceeds :the number of moles of vinyl ester employed, the product-will almost of necessity comprise a mixture ofcompounds. For these reasons the members of the present class of corrosion inhibitors are referred to as reaction products, rather than as definite chemical compounds, with .the preferred products being referred .to as ethylene ,polyamines in'which from 2 to 30f :the amino groups contain a R.CQO- C H substituent.

.As stated above, the members of the present class of corrosion inhibitors-are obtained .by reacting from -1 to -6, preferably from- 2 to 3,-=moles of a vinyl'esterof'a fatty acid-containing from about :12 to 22 carbon atornswith an ethylene polyamine containing from 2 to 6 amino groups. .As examples of the vinyl ester reactant there maybe mentioned vinyl laurate, vinyl myristate, vinyl palmitate, vinyl stearate, vinyl oleate, vinyl linoleate, viny behenate, vinyl linolenate, vinyl .arachidate, etc. Vinyl oleate is preferred. The operable ethylene lpolyamines are ethylene diamine, diethylene triamine, triethylene tetramine, tetra-ethylene pentamine, and pentaethylene hexamine. Mixtures of such ethylene poly amines may also be employed.

The reaction by which the present products are formed takes place spontaneously simply open admixture ofthe 3. two reactants at room temperature. In order to avoid the formation of amides the reaction temperature should be maintained below about 100 C., and in some cases it may be necessary to provide means for cooling-the reaction mixture in order to" avoid exceeding such temperature. Conveniently, the reaction is carried'out in thepresence of an inert liquid reaction medium, e. g., benzene, toluene, kerosene extract, etc., and if desired such solvent may be allowed to remain with the product to facilitate its handling and application to corrosion inhibiting uses. The number of moles of vinyl ester employed per mole of ethylene polyamine should not exceed the number of amino groups present in the ethylene polyamine, i. e., should not exceed x+l moles, and is preferably between about 2 and about 3 moles per mole of ethylene polyamine. When the product contains an average of more than three RCOO--C H groups in the molecule it is too oil-soluble to become effectively distributed in the aqueous phase of the well eflluent without the use of added dispersing agents. Conversely, when the product contains an average of less than two RCOOC H groups in the molecule it is too water-soluble to become elfectively distributed in the oil phase without the use of dispersing agents. From a corrosion inhibiting standpoint, however, the products containing an average of less than two and more than three RCOO-C H groups per mole are highly satisfactory; they are less preferred only because for best results a supplementary dispersing agent should be used.

The following examples will illustrate the preparation of several of the corrosion inhibitors of the present class,

but are not to be construed to limiting the invention.

Example I One mole of ethylene diamine is dissolved in twice its volume of toluene and two moles of vinyl stearate are gradually added to the solution with stirring. During such addition the temperature of the reaction mixture rises to about 60 C. The product so obtained may be used directly as a corrosion inhibiting composition or, if desired, the solvent may be distilled off to obtain the active ingredient as a dark-brown viscous liquid containing an average of two R--COOC H groups in the molecule.

Example II Example I is repeated, substituting vinyl oleate and tetraethylene pentamine for the vinyl stearate and ethylene diamine.

Example III One mole of tri'ethylene tetramine is dissolved in an equal volume of kerosene extract (B. R.=400-600 F.), and 2.5 moles of vinyl oleate are added with stirring while maintaining the temperature at about 40 C. The resulting dark-brown liquid is directly suitable for use as a corrosion inhibitor.

In treating a well to inhibit corrosion therein in accordance with one embodiment of the invention, the inhibitor is simply introduced into the well fluid via the well tubing or casing in an amount suflicient to effect a substantial degree of corrosion inhibition. Such amount will depend primarily upon the nature of the well fluid and the temperature and pressures prevailing within the well, but highly satisfactory results are usually obtained, even under exceptionally adverse conditions, when the weight of inhibitor in the well is maintained between about 0.0001 and about 0.01 percent of the volume of the fluid in the well. As previously stated, the inhibitors of the present class are most conveniently employed in the form of a solution in a suitable solvent.

When the reaction product contains an average of less than about two or more than about three groups in the molecule, it is preferably employed in conjunction with one or more dispersing agents which may or may not have corrosion inhibiting properties of their own. The primary purpose of such agents is to promote uniform dispersion of the inhibitors in the well fluid, and since such fluid comprises both water or brine and oil, the dispersing agent may be either wateror oilsoluble, or both. A mixture of two or more types of dispersing agents may also be employed. A wide variety of both types of dispersing agents is known; and any of them may be employed in preparing corrosion inhibiting compositions comprising the present class of esters as the essential active ingredient. Oil-soluble sulfonic acids, such as the petroleum sulfoni'c acids, and the salts thereof, and nonionic dispersing agents such as the Spans and Tweens and the fatty acid amides are preferred. Compositions of this type ordinarily comprise between about 5 and about 20 percent by weight of the inhibitor, and between 2 and about 10 percent by weight of one or a mixture of dispersing agents with the remainder consisting of an inert solvent. The composition may also contain scale inhibitors such as the polyphosphates and scale-inhibiting acids, and, if desired, dispersing agents may be employed even though the active ingredient contains between about two and about three R-COOC H groups in the molecule.

The following examples will illustrate typical corrosion inhibiting compositions provided by the invention, but are not to be construed as limiting the same.

Example VII Reaction product of 5 moles of vinyl linoleate with 1 mole of tetraethylene pentamine Benzene 90 Sodium petroleum sulfonate 5 Example VIII Reaction product of 2.5 moles of vinyl oleate with 1 mole of diethylene triamine 15 Kerosene extract Reaction product of castor oil fatty acids with diethanolamine 3 Sodium petroleum sulfonate 2 In testing various materials to determine their corrosion inhibiting properties, it has been found that test procedures which are carried out at ordinary tempera tures and pressures do not reflect accurately the behavior of the test compositions in a well. Thus, inhibitors which appear satisfactory when tested by adding the same to an oil well eflluent and thereafter contacting the inhibited eflluent with metal strips at atmospheric temperatures and pressures often prove unsatisfactory when placed in an actual well. Accordingly, I have employed the following rigorous testing method which has been found to simulate actual well conditions to a high degree: Two 6-inch lengths of steel sucker rod are polished with emery, washed, and accurately weighed. These test specimens are then mountedside-by-side on the head of a 4-liter rocking autoclave. Two hundred ml. of kerosene containing several drops of th'e corrosion inhibitor to be tested are then introducedinto the autoclave, and the head is bolted on. The autoclave is then purged with carbon dioxide to remove free air. Three and one-half liters of 3% aqueous sodiumchloride from which dissolved air has been removed by purging with carbon dioxide are then introduced into the autoclave, and the latter is pressured up to about 20 p. s. i. g. with carbon dioxide. The inhibited wellfluid in the autoclave contains about 30 p. p. m. of inhibitor for each drop of the same contained in the 200 ml. ofkerosene solution. Kero sene is employed as the hydrocarbon phase of the simulated well fluid since it isnot known to contain any of the naturally occurring corrosion inhibitors which are present in some crudes. The autoclave and contents are heated at 100-ll0 C. under an autogenic pressure of about 70 p. s. i. g. for 24 hours. Upon completion of the heating period the autoclave is cooled to atmospheric temperature and opened, and the test specimens are removed, washed, and weighed. The efliciency of the inhibitor is calculated as follows:

WI W2 1 where W is the loss in specimen weight (total of both specimens) with an unhibited fluid and W is the loss in specimen weight (total of both specimens) with the inhibited fluid.

The following table sets forth the results obtained when several of the present corrosion inhibitors were tested in accordance with the foregoing procedure:

Percent efficiency X 100 Cone. of Active Ingredient,

p. p. in.

Inhibition Efliciency, percent 1 Reaction product of 75 parts vinyl oleate and 19 parts TEPA dissolved in 461 paits of kerosene extract (B. R.=400600 F.). 8.5 2 Reaction product of 75 parts vinyl oleate and 19 parts 'lEPA dissolved in 94 parts of kerosene extract (B. R.=400600 F.) .l 3 Reaction product of 77 parts vinyl ole-ate and 31.5 parts Polyan-vine H 2 dissolved in 461 parts of kero sene extract (B. R.=400600 F.).. 8.5 4 Reaction product of 30 parts vinyl oleate and 10.5 parts of diethanolamine dissolved in 461 parts of kero sens extract (B. R.=4(10600 F.) 8.5 5 Reaction product of 30 parts of vinyl oleate and 15.7 parts decylamine dissolved in 461 parts of kerosene extract (B. R.=400600 F.) 8.5

1 Tetraethylene pentamine.

B A mixture of higher polyethylene polyamines sold by Carbide and Carbon Chemical Corp.

A comparison of tests l-3 with tests 4 and 5, above, demonstrate that the present class of inhibitors are far superior to the products obtained by reacting vinyl oleate with alkanolamines or simple primary amines.

The foregoing tests were made employing carbon dioxide as the gas phase of the simulated well fluid. When hydrogen sulfide was substituted for the carbon dioxide in test 2, the inhibition efficiency was' 92.4 percent at an active ingredient concentration of 25 p. p. In.

Other modes of applying the principle of my invention may be employed instead of those explained, change being made as regards the methods or the materials employed, provided the composition or steps stated by any of the following claims, or the equivalent of such stated compositions or steps, be obtained or employed.

1, therefore, particularly point out and distinctly claim as my invention:

1. The method for reducing the corrosiveness of oil and gas well fluids comprising moisture and at least one acidic material selected from the class consisting of carbon dioxide and hydrogen sulfide towards ferrous metals under conditions of elevated temperature and pressure which comprises introducing into said well fluid-a corrosion inhibiting amount 051 a product? prepared by reacting a vinyl ester: of a fatty acid containing from 12 to 22 carbon atoms with an ethylene polyamine of the general formula:

NH' (C' H NH) -H.

wherein x represents an integer from I to 5, inclusive, said reaction being. carried outat. atemperature below that at which any substantial amountsof amides are formed and between about 1 and about 6,.but not more than about x+1,.moles of saidvinyl esterbeing; employed per mole of said ethylene polyamine.

2. The process of claim l wherein the said reaction product is introduced into the well fluid in the formof a solution in an. organic solvent.

3. The process of claim 1 wherein the said vinyl ester is vinyl oleate.

4. The process of claim 1 wherein the said reaction product is prepared byreacting between about 2 and about 3 moles of 'vinyloleate with one mole of tetraethylene pentamine.

5. The process of claim 1 wherein the said reaction product is introduced into the well fluid in an amount corresponding to between about 0.0001 and about 0.1 by volume of the fluid.

6. The process of claim 4 wherein the said reaction product is introduced into the well fluid in the form of a solution comprising between about 10 and about percent by weight of said product and between about and about 20 percent by weight of a liquid petroleum hydrocarbon solvent.

7. The method for reducing the corrosiveness of oil and gas well fluid comprising moisture and at least one acidic material selected from the class consisting of carbon dioxide and hydrogen sulfide towards ferrous metals under conditions of elevated temperature and pressure which comprises introducing into said well fluid a corrosion inhibiting amount of an ethylene polyamine of the general formula:

wherein x represents an integer from 1 to 5, inclusive, in which from 2 to 3 of the amino groups bear a substituent of the general formula:

wherein R represents an aliphatic radical containing from ll to 21 carbon atoms.

8. The process of claim 7 wherein the said ethylene polyamine is tetraethylene pentamine.

9. The process of claim 7 wherein R represents the 9-heptadecenyl radical.

10. The process of claim 7 wherein the said product is tetraethylene pentamine in which from 2 to 3 of the amino groups bear a substituent.

11. A corrosion inhibiting composition comprising (1) between about 10 and about 80 percent by weight of a product prepared by reacting a vinyl ester of a fatty acid containing from 12 to 22 carbon atoms with an ethylene polyamine of the general formula:

wherein x represents an integer from 1 to 5, inclusive, said reaction being carried out at a temperature below that at which any substantial amounts of amides are formed and between about 1 and about 6, but not more than x-I-l, moles of said vinyl ester being employed per mole of said ethylene polyamine, and (2) between 7 about 90 and about 20 percent by weight of a liquid petroleum hydrocarbon solvent.

12. A- composition as defined by'claim 11 wherein the said vinyl ester is vinyl oleate.

13. A composition as defined by claim 11 wherein the said vinyl ester is vinyl oleate, said ethylene is tetraethylene pentamine, and between about 2 and about 3 moles of said vinyl ester are employed per mole of said ethylene polyamine.

14. A corrosion inhibiting composition comprising (1) between about and about 20 percent by weight of a product prepared by reacting a vinyl ester of a fatty acid containing from 12 to 22 carbon atoms with an ethylene polyamine of the general formula:

'wherein x represents an integer from 1 to 5, inclusive, said reaction being carried out at a temperature below that at which any substantial amounts of amides are formed and between about 1 and about 5, but not more than x-l-l, moles of said'vinyl ester being employed per mole of said ethylene polyamine, and (2) between about 2 and about percent by weight of an organic dispersing agent, and (3) suflicient of a liquid petroleum hydrocarbon to make 100 percent by weight.

. 15; A composition as defined by claim '14 wherein the said vinyl ester is vinyl oleate and said ethylene polyamine is tetraethylene pentamine.

-16. A corrosion inhibiting composition comprising an inert liquid organic hydrocarbon solvent solution of from 5% to"% by' weight of a product prepared by reacting a vinyl esterof a fatty acid containing from 12 to 22 carbon atoms with an ethylene polyamine of the general formula:

wherein x represents an integer from 1 to 5, inclusive, saidreaction being carried out at a temperature below that at which any substantial amounts of amides are formed and between about 1 and about 6, but not more than x-I-l, moles of said vinyl ester being employed per mole of said ethylene polyamine.

References Cited in the file of this patent UNITED STATES PATENTS 2,520,356 Bishop Aug. 29, 1950 2,598,213 Blair May 27, 1952 2,736,658 *Pfohl et a1 2 Feb. 28, 1956 

1. THE METHOD FOR REDUCING THE CORROSIVENESS OF OIL AND GAS WELL FLUIDS COMPRISING MOISTURE AND AT LEAST ONE ACIDIC MATERIAL SELECTED FROM THE CLASS CONSISTING OF CARBON DIOXIDE AND HYDROGEN SULFIDE TOWARDS FERROUS METALS UNDER CONDITIONS OF ELEVATED TEMPERATURE AND PRESSURE WHICH COMPRISES INTRODUCING INTO SAID WELL FLUID A CORROSION INHIBITING AMOUNT OF A PRODUCT PREPARED BY REACTING A VINYL ESTER OF A FAATTY ACID CONTAINING FROM 12 TO 22 CARBON ATOMS WITH AN ETHYLENE POLYAMINE OF THE GENERAL FORMULA: 